1. Technical Field
This disclosure relates to an electrophotographic photoreceptor, an image forming method using the electrophotographic photoreceptor, an image forming apparatus, and a process cartridge for the image forming apparatus and, in particular, to a photoreceptor including compound semiconductors.
2. Description of the Related Art
In recent years and continuing to the present, the electrophotographic technology has been widely used not only in the field of copiers, but also in the field of various printers and facsimile machines because it can provide images excellent in instantaneousness, quality, and shelf life. An electrophotographic process in the electrophotographic technology basically consists of an image forming process and an initialization process for repetitive use of a photoreceptor, namely, a destaticizing process. In other words, the image forming process includes the steps of uniformly charging the surface of the photoreceptor, forming an electrostatic latent image by image exposure corresponding to an original, developing the electrostatic latent image with toner, and transferring and fixing the toner image to a sheet (the toner image may pass through a transfer body on its way to the sheet in some cases). Furthermore, the destaticizing process includes the steps of cleaning the developer left on the surface of the photoreceptor and removing the residual charges.
Until recently, known photoreceptors playing a central role in the electrophotographic technology have been made of inorganic photoconductive materials such as selenium, arsenic-selenium alloy, cadmium sulfide, and zinc oxide. However, there have been recently developed photoreceptors made of organic photoconductive materials having advantages such as easiness in film deposition and manufacturing without causing environmental pollution. Particularly, so-called laminated type photoreceptors including a charge generation layer and a charge transfer layer are in the mainstream and thus manufactured in quantities because they can provide high sensitivity, a high level of safety due to their wide selection range of materials, and relatively high advantages in terms of costs attributable to increased coating productivity.
Meanwhile, in order to prevent the injection of charges (holes) from a conductive support body to a photosensitive layer, there have been proposed photoreceptors that have an undercoating layer (intermediate layer) whose bottom end of the conductive band ranges from a vacuum level to −3.8 eV or lower and which is made of a semiconductive substance between the conductive support body and the photosensitive layer (Patent Document 1). Examples of the semiconductive substance include titanium oxide, strontium titanate, calcium titanate, tungsten oxide, ferric oxide, bismuth oxide, molybdenum sulfide, and the like.    Patent Document 1: JP-A-2006-11485
In conventional electrophotographic systems, it may be difficult to sufficiently suppress the injection of charges (holes) from the conductive support body to the photosensitive layer with the conventional photoreceptors.